Submerged wave energy converter for deep water operations

Abstract

A submergible wave energy converter and method for using the same are described. Such a wave energy converter may be used for deep water operations. In one embodiment, the wave energy converter apparatus comprises an absorber having a body with an upper surface and a bottom surface and at least one power take-off (PTO) unit coupled to the absorber and configured to displace movement of the absorber body relative to a reference, where the power take-off unit is operable to perform motion energy conversion based on displacement of the absorber body relative to the reference in response to wave excitation, and where the power take-off unit is operable to return the absorber body from a displaced position to a predefined equilibrium position and to provide a force acting on the absorber body for energy extraction.

What is claimed is: 
     
       1. A fully submerged wave energy converter apparatus,
 comprising: 
 an absorber body having positive buoyancy when fully submerged; 
 a first power take-off unit embedded into the absorber body, the first power take-off unit being directly mechanically coupled to a first angled mooring connection, the first angled mooring connection to be anchored to a sea floor; 
 a second power take-off unit embedded into the absorber body, the second power take-off unit being directly mechanically coupled to a second angled mooring connection, the second angled mooring connection to be anchored to the sea floor, the first power take-off unit and the second power take-off unit being operable to perform motion energy conversion based on displacement of the absorber body due to wave excitation, 
 wherein the first power take-off unit and the second power take-off unit extract net positive energy from at least one of surge, sway, heave, roll, and pitch motion of the absorber body. 
 
     
     
       2. The wave energy converter apparatus of  claim 1 , wherein the first power take-off unit, the second power take-off unit, the first angled mooring connection, the second angled mooring connection, and the absorber body extract energy from incident ocean waves in multiple degrees of freedom. 
     
     
       3. The wave energy converter apparatus of  claim 1 , wherein the first angled mooring connection is coupled to a distinct anchor. 
     
     
       4. The wave energy converter apparatus of  claim 1 , further comprising a ballast system to increase or decrease buoyancy of the absorber body. 
     
     
       5. The wave energy converter apparatus of  claim 1 , wherein the first power take-off unit comprises a closed hydraulic system having a cylinder with a piston, wherein linear movement of the piston pressurizes hydraulic fluid to be discharged in a hydraulic motor coupled to an electric generator. 
     
     
       6. The wave energy converter apparatus of  claim 1 , wherein the first power take-off unit comprises a winch drum connected to a rotating shaft, a rack and pinion assembly, a mechanical ball screw, or a magnetic lead screw assembly to convert linear mechanical motion into rotary motion or rotary motion into linear motion. 
     
     
       7. The wave energy converter apparatus of  claim 1 , wherein one of the first power take-off unit or the second power take-off unit comprises a gas-spring comprising a closed hydraulic system including a piston, wherein linear movement of the piston pressurizes fluid in hydraulic accumulators for energy storage or a rotary generator. 
     
     
       8. The wave energy converter apparatus of  claim 1 , wherein one of the first power take-off unit or the second power take-off unit comprises a driven rotary electrical machine, a linear generator assembly, a mechanical spring, a mechanical clutch, or a mechanical brake. 
     
     
       9. The wave energy converter apparatus of  claim 1 , wherein the first power take-off unit and the second power take-off unit extract net positive energy from vertical motion, horizontal motion, and rotational motion of the absorber body. 
     
     
       10. The wave energy converter apparatus of  claim 1 , further comprising an aperture in the absorber to alter total impedance of the apparatus and/or incident ocean wave excitation. 
     
     
       11. The wave energy converter apparatus of  claim 10 , further comprising an aperture control mechanism to open or close the aperture based on a control or environmental input. 
     
     
       12. The wave energy converter apparatus of  claim 11 , wherein the aperture control mechanism comprises a passive control mechanism to open or close the aperture. 
     
     
       13. The wave energy converter apparatus of  claim 1 , further comprising a depth adjustment mechanism to adjust the absorber body's submergence depth based on a control input. 
     
     
       14. The wave energy converter apparatus of  claim 13 , wherein one of the first power take-off unit or the second power take-off unit comprises the depth adjustment mechanism. 
     
     
       15. The wave energy converter apparatus of  claim 1 , further comprising a control system receiving input from sensors, databases and/or an operator to control wave loads and energy output of the apparatus. 
     
     
       16. A wave energy converter apparatus, comprising:
 an absorber body having positive buoyancy when fully submerged; 
 a power take-off unit embedded into the absorber body, the power take-off unit directly coupled to an angled mooring line, the angled mooring line to be anchored to a sea floor, the power take-off unit being operable to perform motion energy conversion based on displacement of the absorber body due to wave excitation, 
 wherein the power take-off unit extracts net positive energy from surge, sway, heave, roll, and pitch motion of the absorber body; and 
 a ballast system to control buoyancy of the absorber body. 
 
     
     
       17. A method for using a wave energy converter apparatus, comprising:
 submerging an absorber, the absorber having a body having an upper surface and a bottom surface, wherein the absorber has a positive buoyancy when fully submerged; 
 extracting energy from incident ocean waves using a first power take-off unit embedded into the absorber body, the first power take-off unit being directly mechanically coupled to a first angled mooring connection, the first angled mooring connection anchored to a sea floor; and 
 extracting energy from incident ocean waves using a second power take-off unit embedded into the absorber body, the second power take-off unit being directly mechanically coupled to a second angled mooring connection, the second angled mooring connection being anchored to the seafloor, wherein the first and second power take-off units perform motion energy conversion based on displacement of the absorber body due to wave excitation, and 
 wherein the first power take-off unit and the second power take-off unit extract net positive energy from at least one of surge, sway, heave, roll, and pitch motion of the absorber body. 
 
     
     
       18. The method of  claim 17 , wherein the first angled mooring connection comprises a mooring line coupled to a distinct anchor on the sea floor.